| 1. |
- Balador, Ali, et al.
(author)
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A Density-Based Contention Window Control Scheme for Unicast Communications in Vehicular Ad Hoc Networks
- 2015
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In: International Journal of Ad Hoc and Ubiquitous Computing. - 1743-8225 .- 1743-8233. ; 24, s. 65-75
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Journal article (peer-reviewed)abstract
- Achieving a well-designed medium access control MAC protocol is a challenging issue to improve communications efficiency due to the dynamic nature of vehicular ad hoc networks VANETs. IEEE 802.11p standard was selected as the best choice for vehicular environments considering its availability, maturity, and cost. The common problem in all IEEE 802.11 based protocols is scalability, exhibiting performance degradation in highly variable network scenarios. Experimental results for the IEEE 802.11-based MAC protocol show the importance of contention window adjustment on communications performance; however the vehicular communications community has not yet addressed this issue in unicast communication environments. This paper proposes a novel contention window control scheme for VANET environments based on estimating the network density, which is then used to dynamically adapt the CW size. Analysis and simulation results show that our proposal provides better overall performance compared with previous proposals, even in high network density scenarios.
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| 2. |
- Balador, Ali, et al.
(author)
-
A Novel 802.11 Contention Window Control Scheme for Vehicular Environments
- 2013
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In: Jornadas Sarteco 2013 JS 2013. - 9788469583302 ; , s. 98-103
-
Conference paper (peer-reviewed)abstract
- Intelligent Transportation Systems (ITS) have attractive potential in order to decrease the ordi- nary traffic jams and avoid transportation disasters. Also, they are able to provide various infotainment services like browsing, reading e-mail or using social networks that makes a trip more interesting. In or- der to make it more efficient in real vehicular envi- ronments, achieving a well-designed Medium Access Control (MAC) protocol is a challenging issue due to the dynamic nature of VANETs, scalability issues, and the variety of application requirements. Differ- ent standardization organizations have selected IEEE 802.11 as the first choice for VANET environments considering its availability, maturity, and cost. The research results for IEEE 802.11 MAC protocol show the importance of contention window adjustment on the communications performance. The impact of ad- justing the contention window has been studied in MANETs, but the vehicular communication commu- nity has not yet addressed this issue thoroughly. This paper proposes e-HBCWC, a new contention window control scheme for VANET environments based on estimating the network condition. Analy- sis and simulation results using OMNeT++ in urban scenarios show that e-HBCWC clearly outperforms 802.11 DCF, even in very high network density, by increasing the packet delivery rate while decreasing the number of collisions and the end-to-end delay for unicast applications.
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| 3. |
- Balador, Ali, et al.
(author)
-
A Reliable and Efficient Token-Based MAC Protocol for Platooning Applications
- 2016. - 12
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In: 12th Swedish National Computer Networking Workshop (SNCNW 2016).
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Conference paper (peer-reviewed)abstract
- Platooning is both a challenging and rewarding application. Challenging since strict timing and reliability requirements are imposed by the distributed control system required to operate the platoon. Rewarding since considerable fuel reductions are possible. As platooning takes place in a vehicular ad hoc network, the use of IEEE 802.11p is close to mandatory. However, the 802.11p medium access method suffers from packet collisions and random delays. Most ongoing research suggests using TDMA on top of 802.11p as a potential remedy. However, TDMA requires synchronization and is not very flexible if the beacon frequency needs to be updated, the number of platoon members changes, or if retransmissions for increased reliability are required. We therefore suggest a token-passing medium access method where the next token holder is selected based on beacon data age. This has the advantage of allowing beacons to be re-broadcasted in each beacon interval whenever time and bandwidth are available. We show that our token-based method is able to reduce the data age and considerably increase reliability compared to pure 802.11p.
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| 4. |
- Balador, Ali, et al.
(author)
-
A Reliable Token-Based MAC Protocol for Delay Sensitive Platooning Applications
- 2015
-
In: 2015 IEEE 82nd Vehicular Technology Conference (VTC2015-Fall). - [S.l.] : IEEE. - 9781479980918 - 9781479980901
-
Conference paper (peer-reviewed)abstract
- Platooning is both a challenging and rewarding application. Challenging since strict timing and reliability requirements are imposed by the distributed control system required to operate the platoon. Rewarding since considerable fuel reductions are possible. As platooning takes place in a vehicular ad hoc network, the use of IEEE 802.11p is close to mandatory. However, the 802.11p medium access method suffers from packet collisions and random delays. Most ongoing research suggests using TDMA on top of 802.11p as a potential remedy. However, TDMA requires synchronization and is not very flexible if the beacon frequency needs to be updated, the number of platoon members changes, or if retransmissions for increased reliability are required. We therefore suggest a token-passing medium access method where the next token holder is selected based on beacon data age. This has the advantage of allowing beacons to be re-broadcasted in each beacon interval whenever time and bandwidth are available. We show that our token-based method is able to reduce the data age and considerably increase reliability compared to pure 802.11p. © 2015 IEEE.
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| 5. |
- Balador, Ali, et al.
(author)
-
A Reliable Token-Based MAC Protocol for V2V Communication in Urban VANET
- 2016
-
In: 2016 IEEE 27TH ANNUAL INTERNATIONAL SYMPOSIUM ON PERSONAL, INDOOR, AND MOBILE RADIO COMMUNICATIONS (PIMRC). - Piscataway : IEEE. - 9781509032549 - 9781509032556 ; , s. 1586-1591
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Conference paper (peer-reviewed)abstract
- Safety applications developed for vehicular environments require every vehicle to periodically broadcast its status information (beacon) to all other vehicles, thereby avoiding the risk of car accidents in the road. Due to the high requirements on timing and reliability posed by traffic safety applications, the current IEEE 802.11p standard, which uses a random access Medium Access Control (MAC) protocol, faces difficulties to support timely and reliable data dissemination in vehicular environments where no acknowledgement or RTS/CTS (Request-to-Send/Clear-to-Send) mechanisms are adopted. In this paper, we propose the Dynamic Token-Based MAC (DTB-MAC) protocol. It implements a token passing approach on top of a random access MAC protocol to prevent channel contention as much as possible, thereby improving the reliability of safety message transmissions. Our proposed protocol selects one of the neighbouring nodes as the next transmitter; this selection accounts for the need to avoid beacon lifetime expiration. Therefore, it automatically offers retransmission opportunities to allow vehicles to successfully transmit their beacons before the next beacon is generated whenever time and bandwidth are available. Based on simulation experiments, we show that the DTB-MAC protocol can achieve better performance than IEEE 802.11p in terms of channel utilization and beacon delivery ratio for urban scenarios.
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| 6. |
- Balador, Ali, et al.
(author)
-
An Efficient MAC Protocol for vehicle platooning in automated highway systems
- 2015
-
In: Jornadas Sarteco 2015 JS 2015. - Cordoba, Spain.
-
Conference paper (peer-reviewed)abstract
- Lately, all the top truck manufacturers are investing considerable resources in the research and development of platooning systems which would allow vehicles to save fuel and improve safety by travelling in a close-following manner. The platooning system requires frequent and reliable vehicle-to-vehicle communications. As platooning takes place in a vehicular ad hoc network, the use of IEEE 802.11p is close to mandatory. However, the 802.11p medium access method suffers from packet collisions and random delays. Most ongoing research suggests using TDMA on top of 802.11p as a potential remedy. However, TDMA requires synchronization and is not very flexible if the beacon frequency needs to be updated, the number of platoon members changes, or if re-transmissions for increased reliability are required. We therefore suggest a token-passing medium access method where the next token holder is selected based on beacon data age. This has the advantage of allowing beacons to be re-broadcasted in each beacon interval whenever time and bandwidth are available. We show that our token-based method is able to reduce the data age and considerably increase reliability considerably compared to pure 802.11p.
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| 7. |
- Balador, Ali, et al.
(author)
-
Congestion Control for Vehicular Environments by Adjusting IEEE 802.11 Contention Window Size
- 2013
-
In: 13th International Conference on Algorithms and Architectures for Parallel Processing ICA3PP-2013. - Cham : Springer International Publishing. - 9783319038889 ; , s. 259-266
-
Conference paper (peer-reviewed)abstract
- Medium access control protocols should manage the highly dynamic nature of Vehicular Ad Hoc Networks (VANETs) and the variety of application requirements. Therefore, achieving a well-designed MAC protocol in VANETs is a challenging issue. The contention window is a critical element for handling medium access collisions in IEEE 802.11, and it highly affects the communications performance. This paper proposes a new contention window control scheme, called DBM-ACW, for VANET environments. Analysis and simulation results using OMNeT++ in urban scenarios show that DBM-ACW provides better overall performance compared with previous proposals, even with high network densities.
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| 8. |
- Balador, Ali, et al.
(author)
-
DTB-MAC : Dynamic Token-Based MAC Protocol for Reliable and Efficient Beacon Broadcasting in VANETs
- 2016
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In: The 13th Annual IEEE Consumer Communications & Networking Conference CCNC 2016. - 9781479963904 ; , s. 109-114
-
Conference paper (peer-reviewed)abstract
- Most applications developed for vehicular environments rely on broadcasting as the main mechanism to disseminate their messages. However, in IEEE 802.11p, which is the most widely accepted Medium Access Control (MAC) protocol for vehicular communications, all transmissions remain unacknowledged if broadcasting is used. Furthermore, safety message transmission requires a strict delay limit and a high reliability, which is an issue for random access MAC protocols like IEEE 802.11p. Therefore, transmission reliability becomes the most important issue for broadcast-based services in vehicular environments. In this paper, we propose a hybrid MAC protocol, referred as Dynamic Token-Based MAC Protocol (DTB-MAC). DTB-MAC uses both a token passing mechanism and a random access MAC protocol to prevent channel contention as much as possible, and to improve the reliability of safety message transmissions. Our proposed protocol tries to select the best neighbouring node as the next transmitter, and when it is not possible, or when it causes a high overhead, the random access MAC protocol is used instead. Based on simulation experiments, we show that the DTB-MAC protocol can achieve better performance compared with IEEE 802.11p in terms of channel utilization and beacon delivery ratio.
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| 9. |
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| 10. |
- Balador, Ali, et al.
(author)
-
Reducing Channel Contention in Vehicular Environments Through an Adaptive Contention Window Solution
- 2013
-
In: IFIP Wireless Days WD 2013. - 9781479905430
-
Conference paper (peer-reviewed)abstract
- Intelligent Transportation Systems (ITS) are attracting growing attention both in industry and academia due to the advances in wireless communication technologies, and a significant demand for a wide variety of applications targeting this kind of environments are expected. In order to make it usable in real vehicular environments, achieving a well-designed Medium Access Control (MAC) protocol is a challenging issue due to the dynamic nature of Vehicular Ad Hoc Networks (VANETs), scalability issues, and the variety of application requirements. Different standardization organizations have selected IEEE 802.11 as the first choice for VANET environments considering its availability, maturity, and cost. The contention window is a critical parameter for handling medium access collisions by the IEEE 802.11 MAC protocol, and it highly affects the communications performance. The impact of adjusting the contention window has been studied in Mobile Ad-Hoc Networks (MANETs), but the vehicular communications community has not yet addressed this issue thoroughly. This paper proposes a new contention window control scheme, called DBM-ACW, for VANET environments. Analysis and simulation results using OMNeT++ in a highway scenario show that DBM-ACW provides better overall performance compared with previous proposals, even with high network densities.
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